High-speed packet access features, like in Universal Mobile Telecommunication System (UMTS), provide for continuous connectivity. An approach for achieving this is User Equipment (UE) Discontinuous Transmission (DTX), which often is referred to as Uplink (UL) Dedicated Physical Control Channel (DPCCH) gating. With UL DPCCH gating, the power control signalling is sent only periodically (gated) to achieve a reduced mode of DPCCH transmissions. This can be made based on whether the UE have any data to send or not.
WO 2006/050443 A1 discloses an approach for selecting a ‘normal activity mode’ or a ‘reduced activity mode’, where the ‘normal activity mode’ means sending DPCCH transmissions in each slot, and ‘reduced activity mode’ means sending DPCCH transmissions, with full power, using e.g. only every fourth slot. The reduced activity mode can reduce interference up to a reduction corresponding to a 6 dB signal-to-interference target reduction. If the UE has not had any data to send for a certain time period, it switches to the reduced activity mode.
The gating scheme can have two different cycles with different cycle length, i.e. a reduced mode and a further reduced mode. For example, UMTS specifies having two such reduced modes. In the given example, after a data transmission on a Dedicated Physical Data Channel (DPDCH), the UE, which may have been in the further reduced operation mode, enters the reduced operation mode, i.e. the cycles between DPCCH transmissions are set to the shorter interval. After some time, preferably set by some timer or after a certain number of DPCCH transmissions, the UE returns to the further reduced operation mode, i.e. the cycles between DPCCH transmissions are set to the longer interval. The UE is kept in this further reduced operation mode until another DPDCH transmission occurs, and the similar process is repeated.
Typically, the further reduced operation mode is configured to have much less intense DPCCH activity. In this operation mode, it is also possible to use a longer preamble than what is available in the other reduced operation mode. This long preamble is supposed to be sufficient to allow power control to adjust before any DPDCH transmission. In case of the shorter interval, i.e. the more intense DPCCH activity, the shorter preamble will suffice.
The two reduced operation modes basically target different transmission scenarios, where the more intense DPCCH activity supports frequent data transmissions with short intervals, and the less intense DPCCH activity supports applications with sporadic or large data volumes. For applications with periodic transmissions, such as Voice over Internet Protocol (VoIP) with Adaptive Multi-Rate (AMR) coding type, the further reduced operation mode is beneficial to use as much as possible. In the given example, voice frames are encoded and transmitted every 20 ms, while Silence Insertion Descriptor (SID) frames are transmitted every 160 ms during silence periods. This implies that, during silence periods, the UE enters the intense DPCCH activity mode every 160 ms and sends a burst of DPCCH frames before it returns to the less activity mode until next SID frame transmission. Similar applies to other data transmission scenarios where sporadic “keep alive” transmissions are present, e.g. some client-server sessions. This not only increases interference; it also increases power consumption of the UE. It is therefore a desire to provide an improved approach for efficient gating.